1. Field of the Invention
This invention relates generally to so-called high lift loaders, and pertains more particularly to loading apparatus of this general character in which the fork carriage mounted at the free end of the telescopic boom assembly can be tilted about a horizontal axis and also extended and retracted in a rectilinear direction.
2. Description of the Prior Art
It has been common practice to tiltably mount a fork carriage at the free end of the telescopic boom assembly. In order to impart horizontal movement to the fork carriage at whatever elevation it has been moved into, such an arrangement involves the movement of the vehicle or tractor in order to position the forks of the carriage relative to an elevated location where a load is to be deposited or removed, as the case may be.
Since the vehicle is mobile, it being contemplated that it be moved from one vantage point to another, the cost of manufacturing a vehicle with a telescopic boom assembly and a tiltable fork carriage thereon is not increased. However, it is difficult to move the vehicle in increments accurate enough in every situation. This becomes particularly troublesome where the load is out of sight as far as the operator is concerned.
The foregoing problem has been recognized and has been generally corrected by providing longitudinally directed tracks or rails on the chassis along which a transfer carriage is reciprocated. While the arrangement just alluded to has worked well in actual practice, nonetheless the initial cost of the equipment has been substantially increased. Also, greater power requirements are necessary inasmuch as a relatively large mass must be shifted back and forth. Nonetheless, this is a decided improvement over the earlier prior art in which the vehicle itself must be moved back and forth.
A problem common to both prior art situations is that frequently the load must be placed on an upper floor or roof of a building under construction. A vertical wall can offer interference and whether the entire vehicle is moved or whether a transfer carriage is employed can interfere with the placement of the load, for there will be interference between the boom assembly and the wall, thereby necessitating that the load be placed near the wall whereas it is frequently desirable to place the load as far inwardly from the wall as possible.
At any rate, an example of the prior art referred to above in which a transfer carriage is moved along longitudinally disposes tracks on the vehicle is described in U.S. Pat. No. 4,147,263, issued Apr. 3, 1979, to Sherman B. Frederick et al for "High Lift Loader With Extended Transfer".